1. Field of the Invention
The present invention relates to optical coupling elements disposed between an optical fiber and an optical element so as to optically couple the optical fiber and the optical element, and to optical coupling units equipped with such optical coupling elements. In particular, the present invention relates to an optical coupling element and an optical coupling unit in which an optical coupling portion is free of a multilayer structure.
2. Description of the Related Art
Optical coupling elements that optically couple an optical fiber and an optical element, such as a light-emitting element or a light-receiving element, have been known. In addition, optical coupling units that include such an optical coupling element and a holding member that holds the optical coupling element and the optical fiber have also been known. An optical coupling element is capable of coupling light from the optical fiber to the optical element or light from the optical element to the optical fiber at high efficiency. An example of an optical coupling unit configured to have a lens disposed between an optical fiber and an optical element for the purpose of optical coupling is disclosed in Japanese Unexamined Patent Application Publication No. 7-134225.
Another known example of an optical coupling element only has an optical coupling function and is separately provided with a component such as a lens. In this case, the optical coupling element can have a simple cylindrical shape, but will require a multilayer structure including two layers which are a core layer and a cladding layer if bidirectional light transmission is desired.
However, since optical coupling elements having such structures are formed by joining together two different components, such optical coupling elements are problematic in view of high costs. On the other hand, if an optical coupling element is to be formed by resin molding, it is difficult to perform the molding process stably since the optical coupling element has a linear form.